Thursday, January 14, 2010

Mars Coming to Opposition, Won't be Size of the Full Moon

Mars on January 12. It has a long way to go in 2 weeks to be the size of the full moon.

Later this month, Mars will be coming to opposition, which is when Mars is directly opposite the Sun in the sky as seen from Earth, so Mars rises and sets opposite the Sun, making for an all night event.. Because of the straight alignment of Sun, Earth, Mars, this is the point in time where Mars makes its closest approach to Earth.

This time, the approach won't be too close, with the planets only coming within about 61 million miles of each other. Still, the change in Mars' brightness will be apparent. Of all the planets, Mars has the most elliptical (oval-like) orbit. This results in dramatic changes in brightness. At its farthest from earth, Mars shines at about +1.3 magnitude. When Mars made its very close 2003 approach, it was up to -3 magnitude, or about 40 times brighter than at its dimmest when the planet came to about 34 million miles from Earth.

This year, opposition will occur on January 27 with the planet peaking in brightness at around -1.3 magnitude, about as bright as the brightest star in our sky, Sirius. Obviously, this is not nearly as large or as bright as the full moon, which lights up the sky at -12 magnitude.This opposition will also mark the first time since 1994 that missions to Mars haven't been launched at this close approach. Both the American Mars Science Laboratory and Russian Phobos-Grunt probes are being put on hold until the next opposition in 2012.

Still, don't be dismayed at the fact that this opposition will not be one of the best. Due to the timing, Mars will be very high in the sky, which is great for high-power telescope observing, which was anything but the case for the “great” 2003 approach. Unfortunately, don't expect to see any trees on Mars.

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